upstream-rocketchat/apps/meteor/client/views/room/providers/hooks/useInstance.spec.ts

import { renderHook } from '@testing-library/react';

import { useInstance } from './useInstance';

class MockChatMessages {
	release() {
		return 'released';
	}
}

describe('useInstance', () => {
	let factory: jest.Mock;
	let release: jest.Mock;

	beforeEach(() => {
		jest.clearAllMocks();

		release = jest.fn();
		factory = jest.fn().mockReturnValue([{ instance: new MockChatMessages() }, release]);
	});

	it('should create a new instance when dependencies change', () => {
		const { result, rerender } = renderHook(({ deps }) => useInstance(factory, deps), {
			initialProps: { deps: ['initial-dep'] },
		});

		expect(result.current).toEqual({ instance: new MockChatMessages() });
		expect(factory).toHaveBeenCalledTimes(1);
		expect(release).toHaveBeenCalledTimes(0);

		rerender({ deps: ['new-dep'] });

		expect(result.current).toEqual({ instance: new MockChatMessages() });
		expect(factory).toHaveBeenCalledTimes(2);
		expect(release).toHaveBeenCalledTimes(1);
	});

	it('should not create a new instance when dependencies do not change', () => {
		const { result, rerender } = renderHook(({ deps }) => useInstance(factory, deps), {
			initialProps: { deps: ['initial-dep'] },
		});

		expect(result.current).toEqual({ instance: new MockChatMessages() });
		expect(factory).toHaveBeenCalledTimes(1);
		expect(release).toHaveBeenCalledTimes(0);

		rerender({ deps: ['initial-dep'] });

		expect(result.current).toEqual({ instance: new MockChatMessages() });
		expect(factory).toHaveBeenCalledTimes(1);
		expect(release).toHaveBeenCalledTimes(0);
	});

	it('should call release function when component unmounts', () => {
		const { unmount } = renderHook(() => useInstance(factory, ['initial-dep']));

		unmount();

		expect(release).toHaveBeenCalledTimes(1);
	});
});